It is well understood by those skilled in the semiconductor art that a III-V semiconductor compound is one which includes elements from group III and V of the Periodic Table of Elements.
Many III-V heterojunction devices, such as transmission photocathodes and lasers, depend greatly on high quality, defect-free interfaces for good performance. Even after defect-free interfaces have been obtained, thermal decomposition can still severely limit device properties. It has been discovered that many III-V heretojunction devices, and in particular lasers grown by vapor phase epitaxial techniques, have suffered from thermal decomposition at the interfacial regions. The thermal decomposition results in defects in the deposition body in the area of the deposition surface which causes reduced device efficiency and reduced device lifetime.
The vapor phase growth of many multi-layered III-V hetetojunction devices typically include the preheating of the depositing body and deposition surface at the temperature used for deposition of the growth layer. Typically, for material such as indium gallium arsenide and gallium arsenide phosphide, this temperature is about 700.degree.. It is believed that those skilled in the art did not realize that preheating of III-V materials like indium gallium phosphide or gallium arsenide phosphide to a temperature of 700.degree. C. would cause thermal decomposition. Applicants have found from studying transmission electron micrographs that there is thermal decomposition at the decomposition surface. The thermal decomposition produces many dislocation loops in the area of the deposition surface which in turn degrade minority carrier device properties. These discoloration loops are due to incongruent evaporation at the deposition surface during the preheating cycle. Therefore, the elimination of this thermal decomposition problem would improve semiconductor device performance and would in general be most desirable in the semiconductor device field.